Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

In radiotherapy, it is essential to have an alternative dosimetric system to identify possible errors at some stage of the process. The optically stimulated luminescence (OSL) technology represents a great advance in the detection of radiation in different areas, one of them being in the area of clinical dosimetry. Objective: To implement an alternative dosimetric system, based on OSL technology of carbon-doped aluminum oxide crystals.  Material and methods: Al2or3:C detectors called "nanodot", MicroStar reader, ionization chambers (Standard Imaging and PTW Freiburg), electrometers (PTW-Freiburg and MNCNP) and other accessories.  Results: The dosimetric - algorithmic procedure, developed for the calculation of the adsorbed dose in the tumor volume, reproduces the dose values with uncertainties less than 2% for a confidence level of 95% and with relative differences less than 5% compared to the values of the absorbed doses prescribed and / or foreseen in radiotherapy treatments.  Conclusions: The nanodot detectors  represent a viable alternative for the verification of the absorbed dose in the patient during radiotherapeutic practice for the verification of the prescribed dose and imparted by in vivo dosimetry. Its quality to preserve the information, as a physical witness of the procedure, contributes to security in the treatments.

The objective of this work is the design of a prototype of a pneumatic centrifugal concentrator that allows small-scale mining that takes place in desert and isolated places, to process ultrafine gold minerals in situ, cleanly, without the use of water and chemical reagents. A mathematical model based on the physico-phenomenological analysis of the differential sedimentation separation mechanism was applied in a film of laminar flow fluid, to determine the particle trajectory inside the bowl of the centrifugal concentrator as a function of the variables of bowl geometry, operating variables and physical characteristics of the particle and fluid. The simulations carried out showed a remarkable effect of the use of air instead of water on the trajectory of the particles within the fluid film. The results also showed that the capacity of the concentrator for the separation of particles by density difference rather than by size difference, was favored when applying low rotation speeds, high air feed rates and for particle sizes in the ultrafine range (< 40 μm). The prototype built will allow to carry out experimental laboratory tests that complement the understanding of the process and refine the design of the concentrator.

Currently, textile processing plants need to control the conditions associated with the spinning process, being the air conditioning of working environments an important factor in the quality and productivity of these processes. The benefits obtained from the optimization of this air conditioning help to guide a lower energy consumption, helping to improve the positioning of the products and providing profitability in the operation processes. Due to the advantages obtained in the air conditioning process, this work proposes a system that allows reusing the residual energy generated at the outlet of the ventilation ducts. This residual energy is fed into the plant to reduce the high temperatures observed in the ceiling. Consequently, this approach will generate a decrease in the service demand of the air conditioning system and reduce operating costs. Also, to verify this proposal, a multiphysics numerical simulation is performed and compared to a conventional air conditioning system. The simulation incorporates turbulence models to represent the flow in the ventilation ducts. In addition, this simulation considers the heat transfer that is generated by the equipment operating in this textile plant. The results of the multiphysics simulation show the temperature fields, flow lines, among other important data obtained from the numerical simulation. All the results are given for a section of the environment of these plants and verify the efficiency of the proposal of this work.

Lima, the capital of Peru, has not suffered from a great earthquake since 1746, making this a prone Mw 8.8 earthquake area according to seismological studies. In this context, seismic structural health monitoring presents an opportunity to assess rapidly buildings after a great earthquake and protect inhabitant from those buildings with high risk of collapse due to aftershocks. A basic seismic structural health monitoring arrangement of a fifteenth-floor residential building is presented using a low-cost sensor called Raspberry Shake 4D. The implemented sensor incorporates both a vertical velocity geophone and three orthogonally positioned microelectromechanical systems accelerometers. The building is a reinforced concrete shear walls structure located in Comas, north of Lima. More than thirty seismic events have been recorded, including the Mw 8.0 Lagunas earthquake (05/26/2019) and the Mw 5.8 (22/06/2021) with epicentral distances of 709 km and 94 km, respectively. Acceleration as high as 150 cm/s2 and as low as 2 cm/s2 have been recorded. It was possible to obtain fundamental frequencies of vibration in longitudinal and transversal directions of the building from the response calculated using the wavelet transform that have a good agreement with results of microtremor measurements performed at different floors. The computed scalograms for seismic records showed important values of energy amplitudes for the fundamental frequencies of the building. Finally, theoretical fundamental frequencies were obtained from a 3D finite element model and an elastic analysis.

In active seismic zones, such as the Peruvian coast, tools for predicting the potential negative impacts of earthquakes are essential for planning mitigation, emergency, and recovery of transportation facilities. For instance, the capacity of a road bridge network after a seismic event to carry traffic flow depends on the degree of expected damage and the related repair costs and downtime. This paper determines the degree of vulnerability of highway bridges to the action of probable earthquakes during the structure's lifetime by applying the capacity spectrum assessment method known as FRACAS (FRAgility through CApacity Spectrum assessment). This approach allows fragility curves to be obtained from analyzing a structure subjected to a series of seismic records of different characteristics. In this way, the method can explain the effect of variability in seismic demand and structural characteristics on the damage statistics simulated for the type of structure and evaluate the associated uncertainty in predicting fragility. As a case study, it is applied the methodology described in the evaluation of the Moche bridge, located in the region of La Libertad (Peruvian coast), which is in an Operational damage state according to an in situ inspection. From the seismic vulnerability assessment, it is obtained that until earthquakes with accelerations of 1.7g, the Moche bridge has a 60% probability of incursion into a Life Safety damage state, being the probability of incursion into a Collapse damage state less than 10%. This methodology is recommended to determine the reliability of bridges, considering the cumulative damage due to probable seismic events during the bridges' lifetime.

Seismic response analyses are performed using a minimum number of seismic records as input motions in order to achieve a statistically strong estimation. Unfortunately, the available information recorded from the current seismic networks is still scarce regarding events with considerable magnitude. In this context, the Random Vibration Theory (RVT) arises as an alternative tool for performing site response analyses without the need of seismic records, since it only requires adequate probabilistic seismic hazard assessment. In this study, RVT was applied to three shear-wave velocity profiles in Lima city with distinct geomorphological origin. These profiles are characteristic for gravelly, sandy and fine deposits so the influence of each soil type in their corresponding transfer function was taken into account. In that sense, the three RVT-based normalized response spectra show good agreement with the design spectra specified in the Peruvian code, despite some amplification in the short (below 0.10 s) and long (above 0.80 s) period ranges related to noise or far-field effects. Furthermore, RVT-based response spectra for La Punta and Villa el Salvador show good agreement with the time-series based analyses from a previous study. In addition, spectral acceleration values surpass those specified in the Peruvian code for a range beyond the corner period. This could suggest that the soil profile characterization based on the time-averaged shear wave velocity from the upper 30 m might be insufficient to evaluate the overall seismic behavior of a soil deposit. Therefore, additional parameters that account for the deeper soil substructure might be required.

Structural Health Monitoring (SHM) allows assessing the structural damage in observed buildings through different methodologies, which observe changes in the structural behavior immediately after an earthquake. Some methodologies assess the structural damage by observing its global capacity curve obtained through the displacement and acceleration in all stories, calculated using wavelet transform and double integration process. Due to limited resources, some floors are instrumented, and non-instrumented stories response could be estimated by additional procedures, for instance the spline shape function. In this paper, different arrangements of sensors in the Edgardo Rebagliati Martins Hospital (HERM) are evaluated to find the best possible configuration to estimate the global capacity curve and the interstories capacity curves. A 14-story building in the HERM is analyzed, and the optimal arrangement to estimate the capacity curve for each interstory capacity curve was using 7 sensors, and 4 sensors were sufficient to estimate the global capacity curve of this building.

Strong motion records are important for improving seismic design, damage assessment and analysis of earthquake effects. Despite the relevance of having strong motion networks, their implementation in Peru has been performed in the very recent years. For instance, only five strong motion stations in Lima recorded the 2007 Mw 7.9 Pisco earthquake, whereas 55 stations recorded the 2021 Mw 6.0 Mala earthquake. The current number of instrumentations in Lima city provides an opportunity to improve soil characterization. This study aims to determine the dominant frequency (fd) of the seismic stations located in Metropolitan Lima. The procedure we adopted, first considered collecting, for an arbitrary station, all the available events recorded from 2011-2021, including the 2007 Mw 7.9 Pisco earthquake. Then, the pseudo spectral acceleration, using 5% damping, for each component were computed, and the horizontal-to-vertical (H/V) spectral ratios were calculated. Finally, the average H/V spectral ratio was used to adequately characterize the values of fd . In total, we evaluated 51 stations throughout Lima city. Values of  fd lower than 1 Hz were observed for the coastal areas in which the underlying soil consist of clayey/sandy deposits and regions with an important impedance contrast in the deeper part of the substructure. These values increment towards the center of the city coinciding with surficial gravel deposits.

Underground structures serve as means of carrying out essential activities in a modern society; therefore, their proper seismic performance is important in the mitigation of the risk of disasters. This work addresses the seismic effects on underground structures in highly seismic areas such as the coast of Perú. The software FLAC was used to perform dynamic analyses of underground structures with rectangular section, using free-field type boundary conditions, accounting for the nonlinear inelastic behavior of the soil, under seven earthquakes matched to the same target spectrum. The analyses were carried out for different earthquake intensities, varying the soil characteristics (homogeneous or stratified) and the geometry of the structure. The results show that when the structure is placed in a homogeneous soil the forces and displacements have only small variations. However, when it is placed in a heterogeneous soil, the results show important differences. Thus, matching to the same target spectrum does not imply a uniform seismic demand. The geometry of the structure and the wall thickness have considerable influence. In heterogeneous soils a relatively flexible structure may experience large deformations and important damage.

Concrete is one of the main building materials in Peru and worldwide, the study of its mechanical properties and concrete mix elaboration have been extensively developed over time. In the last years, new ways of elaboration with different materials have been searched, in order to improve its mechanical properties, including the fiber reinforced concrete. The study of its strain-stress mechanical properties of fiber reinforced concrete under monotonic load is the objective of this investigation, based on experimental tests performed in 90 samples, taking into account the influence of many factors, such as: Compression strength design, sample section geometry (square or circular section), slenderness (height/depth ratio), and the comparison of the reinforced concrete with its equivalent plain concrete in terms of mix design. From the experimental results, the use of fiber reinforcement increases the deformation capacity of the concrete under monotonic compression, but its resistance is not improved significantly. On the other hand, square section specimens have a higher deformation capacity for slenderness 1:2 and 1:3 in comparison with circular section specimens.